Bacterial solute uptake and efflux systems.

The recent discovery of binding protein dependent secondary transporters and the ever-growing family of membrane potential generating secondary transporters emphasize the diversity of transport systems in both the mechanistical and physiological sense. The vast amount of data on the lactose permease is now beginning to crystallize in a model that relates functional events to structural changes of the protein. Evidence has been presented that multidrug transporters pick up their substrates from the membrane, and the binding of a number of substrates to the binding-protein components of ATP-driven transporters is now understood in detail.